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2002-06-11
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C
C PAGE 208-209: NUMERICAL MATHEMATICS AND COMPUTING, CHENEY/KINCAID, 1985
C
C FILE: NGAUSS.FOR
C
C NAIVE GAUSSIAN ELIMINATION TO SOLVE LINEAR SYSTEMS (NGAUSS)
C
PARAMETER (IA = 15)
DIMENSION A(IA,IA),X(IA),B(IA)
DO 4 N = 10,15
DO 3 I = 1,N
DO 2 J = 1,N
A(I,J) = REAL(I+1)**(J-1)
2 CONTINUE
B(I) = (REAL(I+1)**N - 1.0)/REAL(I)
3 CONTINUE
CALL NGAUSS(N,A,IA,B,X)
PRINT 5,N,(X(I),I=1,N)
4 CONTINUE
5 FORMAT(//,'N = ',I2,//,(2X,3E22.14))
STOP
END
SUBROUTINE NGAUSS(N,A,IA,B,X)
DIMENSION A(IA,N),B(N),X(N)
DO 4 K = 1,N-1
DO 3 I = K+1,N
XMULT = A(I,K)/A(K,K)
DO 2 J = K+1,N
A(I,J) = A(I,J) - XMULT*A(K,J)
2 CONTINUE
A(I,K) = XMULT
B(I) = B(I) - XMULT*B(K)
3 CONTINUE
4 CONTINUE
X(N) = B(N)/A(N,N)
DO 6 I = N-1,1,-1
SUM = B(I)
DO 5 J = I+1,N
SUM = SUM - A(I,J)*X(J)
5 CONTINUE
X(I) = SUM/A(I,I)
6 CONTINUE
RETURN
END